A silicone composition polymerized by a chemical reaction which is caused by moisture in the air is well known, and it is used for a sealing agent, an adhesive agent, a coating agent, and a potting agent. By containing a silicon atom with a hydrolyzable functional group, the silicone composition forms a siloxane bond which is caused by moisture in the air. Accordingly, since the composition is cured upon exposure to the air after coating an adhesive agent, it does not require energy like heating or light irradiation and is advantageous from the viewpoint of environment and cost.
Meanwhile, so-called modified silicone such as a vinyl-based polymer with a silicon having a hydrolyzable functional group at the end, is also used as a moisture-curing resin.
Thus, a vinyl-based polymer having at least one cross-linkable silyl group (hydrolyzable group) is known, and use of (meth)acrylic acid or (meth)acrylate ester as a vinyl-based polymer is known, in particular. Furthermore, according to the technique described in JP 2001-011321 A, by adding to a vinyl-based polymer dimethylpolysiloxane having a cross-linkable silyl group at the end, surface tack of a cured product can be lowered. In this regard, it is believed that, because only a soft cured product is obtained from a vinyl polymer alone, an effect of improving the surface curability can be obtained by adding, as a measure to deal with the problem, cross-linkable dimethylpolysiloxane. Furthermore, although it is described in JP 2001-011321 A that the cured state on a surface of a cured product can be improved, there are no descriptions at all regarding the physical properties of a cured product and it is only described to have heat resistance. As such, although there is no mention in JP 2001-011321 A regarding durability of various physical properties (e.g., hardness, tensile strength, or the like), from the viewpoint of practical use like mounting in a vehicle or the like, further improvement of the durability of various physical properties is required.
In this regard, as a well-known problem of a de-alcohol type moisture-curing composition, it is known that foaming is caused, during an durability test involved with exposure to high temperature (atmosphere with 150° C.), by alcohol accumulated in the inside, which is generated from a cross-linkable silyl group. In particular, when a composition is introduced by potting (resin coating) or the like, there is a tendency that foaming is caused by residual alcohol after durability test. There is a problem that foaming of a cured product leads to cracking or fracture, yielding a possibility of having a great loss of oil resistance or sealing property.